Sequence of images recorded by the LASCO C2 coronagraph showing the big
coronal mass ejection of April 7, 1997 (see also EIT image eit022.gif
and the special page of the April 7-9 event at
http://www-istp.gsfc.nasa.gov/istp/cloud_apr97). A coronagraph is a
device to observe the faint outer solar atmosphere by blocking out the
brightness of the sun itself. The circle in the images shows where the
sun would be if it wasn't blocked out. The first frame shows the corona
just before the eruption. The first stage of the eruption is seen in
the upper right-hand corner. The eruption proceeds into a "halo"
event: in the fourth image one can see a brightening around the entire
sun, instead of in just one direction. Material ejected in this event
reached the Earth in the night of April 10-11. A significant amount of
geomagnetic activity was observed in northern regions all over the
world, reaching as far south as New Hampshire and Montana.